Gold(i) complexes with anticancer properties and methods of use thereof

ABSTRACT

Monomeric and dimeric gold(I) complexes as anticancer agents. The gold(I) complexes are coordinated to mixed ligands: one phosphine-based ligand that may be monodentate or bidentate and at least one dithiocarbamate-based ligand that is monodentate. Pharmaceutical compositions incorporating the gold(I) complexes, methods of synthesis, methods of treating cancer and methods of inhibiting cancer cell proliferation and inducing cancer cell apoptosis are also provided.

BACKGROUND OF THE INVENTION

Technical Field

The present invention relates to gold(I) complexes with anticancer orantitumor properties. More specifically, these gold(I) complexes can beeither mono- or binuclear and each gold atom is coordinated to mixedligands having different functional groups.

Description of the Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

The use of cisplatin and its analogues such as oxaliplatin andcarboplatin as metal-based anticancer drugs is well acknowledged in thefield of chemotherapy [B. Rosenberg, L. Van Camp and T. Krigas, Nature,205 (1965) 698; N. Cutillas, G. S. Yellol, C. de Haro, C. Vicente, V.Rodriguez and J. Ruiz, Coord. Chem. Rev., 257 (2013) 2784; {hacek over(Z)}. D. Bugar{hacek over (c)}ić, J. Bogojeski, B. Petrović, S.Hochreuther and R. Van Eldik, Dalton. Trans., 41 (2012) 12329; C.Vetter, C. Wagner, J. Schmidt and D. Steinborn, Inorg. Chim. Acta, 359(2006) 4326; A. Casini and L. Messori, Curr. Top. Med. Chem. 11 (2011)2647; E. Marta Nagy, L. Ronconi, C. Nardon and D. Fregona, Mini-Reviewsin Med. Chem., 12 (2012) 1216—each incorporated herein by reference inits entirety]. These drugs have been used for the treatment of cancerpatients worldwide. However, it is also known that cisplatin and itsanalogues have serious side effects, such as oto-, neuro-, andnephrotoxicity, which decrease its effectiveness in cancer therapy [S.Ahmad, A. A. Isab and S. Ali, Transition Met. Chem., 31 (2006) 1003; S.R. McWhinney, R. M. Goldberg and H. L. McLeod, Mol. Cancer Ther., 8(2009) 10; W. Liu and R. Gust, Chem. Soc. Rev. 42 (2013) 755; X. Yao, K.Panichpisal, N. Kurtzman, and K. Nugent, Am. J. Med. Sci., 334 (2007)115—each incorporated herein by reference in its entirety].Consequently, gold(I) and gold(III) complexes had been investigated asnon-platinum based anticancer candidates [S. S. Al-Jaroudi, M.Monim-ul-Mehboob, M. Altaf, M. Fettouhi, M. I. M. Wazeer, S. Altuwaijriand A. A. Isab, New J. Chem., (2014), DOI:10.1039/c3nj01624b; S. M.Janković, A. Djeković, {hacek over (Z)}. D. Bugar{hacek over (c)}ić, S.V. Janković, G. Lukić, M. Folic and D. {hacek over (C)}anović,Biometals, 25 (2012) 919; S. S. Al-Jaroudi, M. I. M. Wazeer, A. A. Isaband S. Altuwaijri, Polyhedron, 50 (2013) 434; R. B. Bostancioglu, K.Isik, H. Genc, K. Benkli and A. T. Koparal, J. Med. Chem., 27 (2012)458—each incorporated herein by reference in its entirety].

The study of gold complexes, bearing different functional ligandsexhibiting physical, chemical, biological and pharmacologicalproperties, has gained much attention [S. S. Al-Jaroudi, M.Monim-ul-Mehboob, M. Altaf, M. Fettouhi, M. I. M. Wazeer, S. Altuwaijriand A. A. Isab, New J. Chem., (2014), DOI:10.1039/c3nj01624b; S. M.Janković, A. Djeković, {hacek over (Z)}. D. Bugar{hacek over (c)}ić, S.V. Janković, G. Lukić, M. Folic and D. {hacek over (C)}anović,Biometals, 25 (2012) 919; S. S. Al-Jaroudi, M. I. M. Wazeer, A. A. Isaband S. Altuwaijri, Polyhedron, 50 (2013) 434; R. B. Bostancioglu, K.Isik, H. Genc, K. Benkli and A. T. Koparal, J. Med. Chem., 27 (2012)458—each incorporated herein by reference in its entirety]. The gold(I)complexes have been studied as anti-arthritic and anti-microbial agents[O. Crespo, V. V. Brusko, M. C. Giameno, M. L. Tornil, A. Laguna and N.G. Zabirov, Eur. J. Inorg. Chem., (2004) 423; K. Nomiya, R. Noghuchi andM. Oda, Inorg. Chim. Acta, 298 (2000) 24; H.-Q. Liu, T.-C. Cheung, S.-M.Peng and C.-M. Che, J. Chem. Soc., Chem. Comm., (1995) 1787; C. J.O'Connor and E. Sinn, Inorg. Chem., 17 (1978) 2067; M. A. Cinellu, G.Minghetti, M. V. Pinna, S. Stoccoro, A. Zucca, and M. Manassero, J.Chem. Soc., Dalton Trans., (1998) 1735—each incorporated herein byreference in its entirety]. For instance, the drugs like Auranofin,Solganol and Myocrisin have frequently been used for the treatment ofrheumatoid arthritis [S. H. van Rijt and P. J. Sadler, Drug DiscoveryToday, 14 (2009) 1089; R. Noghuchi, A. Hara, A. Sugie and K. Nomiya,Inorg. Chem. Comm., 9 (2006) 355; K. Nomiya, R. Noghuchi, K. Ohsawa, K.Tsuda and M. Oda, J. Inorg. Biochem., 78 (2000) 363; B. P. Howe,Met.-Based Drugs., 4 (1997) 273; J. Ctalano and A. O. Etogo, J.Organomet. Chem., 690 (2005) 6041—each incorporated herein by referencein its entirety]. Interestingly, the extensive cell-based (in vitro) andanimal (in vivo) studies have revealed the potent anti-cancer activitiesof diverse classes of gold(I) and gold(III) complexes with a wide rangeof ligands against a panel of human cancer cell lines [J. C. Lima and L.Rodriguez, J. Med. Chem., 11 (2011) 921; C-M Che and R. W-Y. Sun, Chem.Commun., 47 (2011) 9554; P. Calami, A. Carotti, T. Guerri, L. Messori,E. Mini, P. Orioli and G. P. Speroni, J. Inorg. Biochem., 66 (1997)103—each incorporated herein by reference in its entirety].

Bridged di-gold(I) complexes existing in a linear 2-coordinateconfiguration like [ClAu(P—P)AuCl] (where P—P is a bisphosphine), tendto be more effective than free ligands and such complexes also tend toexhibit a broad range of anticancer activity [R. K. Johnson, C. K.Mirabelli, L. F. Faucette, F. L. McCabe, B. M. Sutton, D. L. Bryan, G.R. Girard and D. T. Hill, Proc. Amer. Assoc. Cancer Res., 26 (1985) 254;C. K. Mirabelli, L. F. Faucette, F. L. McCabe, B. M. Sutton, D. L.Bryan, G. R. Girard, D. T. Hill, J. O. Bartus, S. T. Crooke and R. K.Johnson, J. Med. Chem., 30 (1987) 2181—each incorporated herein byreference in its entirety]. This has inspired the synthesis of stable4-coordinate digold(I) diphosphine complexes [S. J. Berners-Price, M. A.Mazid and P. J. Sadler, J. Chem. Soc., Dalton Trans., (1984) 969; S. J.Berners-Price and P. J. Sadler, Inorg. Chem., 25 (1986) 3822; D. T.Hill, G. R. Girard, U.S. Pat. No. 4,755,611, July 1988—each incorporatedherein by reference in its entirety]. The effect of structural variationin chelated bis(diphosphine) gold(I) complexes [Au(R₂P(CH₂)_(n)PR₂)]X ontheir cytotoxicity and activity against P388 leukaemia, B16 melanoma andM5076 reticulum cell sarcoma has been studied [G. F. Rush, D. W. Albers,P. Meunies, K. Leffler, P. F. Smith, Toxicologist, 7 (1987)59—incorporated herein by reference in its entirety]. J. W. Faamaua etal. reported compounds of general formula [(Ph₂P(CH₂)nPPh₂)(AuS₂CNR₂)₂],n=1, 2 or 3 and R=Et or c-hexyl [J. W. Faamaua and E. R. T. Tiekinka, J.Coord. Chem., 31(2) (1994) 93—incorporated herein by reference in itsentirety].

Since the first decade of 21^(st) century, a new class of gold complexeswith dithiocarbamate ligands has emerged as anticancer agents. In thisregard, Fregona and coworkers synthesized and characterized some novelgold(III) compounds containing N,N-dimethyldithiocarbamate and ethylsarcosine dithiocarbamate exhibiting potential chemical and biologicalprofile [L. Ronconi, L. Giovagnini, C. Marzano, F. Bettio, R. Graziani,G. Pilloni, and D. Fregona, Inorg. Chem., 44 (2005) 1867—incorporatedherein by reference in its entirety].Dibromo(N,N-dimethyldithiocarbamato)gold(III) also showed a noteworthyinhibition of in-vivo MDA-MB-231 breast cancer growth [V. Milacic, D.Chen, L. Ronconi, K. R. Landis-Piwowar, D. Fregona and Q. P. Dou, CancerRes., 66 (2006) 10478—incorporated herein by reference in its entirety].Zhang et al. reported that gold(I)-dithiocarbamato species, namely[Au(ESDT)](2) could hamper the chymotrypsin-like activity of purified20S proteasome and 26S proteasome in human breast cancer MDA-MB-231cells, resulting in accumulation of ubiquitinated proteins andproteasome target proteins, and induction of cell death [X. Zhang, M.Frezza, V. Milacic, L. Ronconi, Y. Fan, C. Bi, D. Fregona and Q. P. Dou,J. Cell Biochem., 109 (2010) 162—incorporated herein by reference in itsentirety]. Recently, the modern research has progressively targeted insearch of new gold(I) complexes as potential anticancer drugs [S. Ahmad,A. A. Isab, S. Ali and A. R. Al-Arfaj, Polyhedron, 25 (2006) 1633; D. V.Partyka, T. J. Robilotto, M. Zeller, A. D. Hunter, T. G. Gray, Proc.Natl. Acad. Sci., (USA) 105 (2008) 14293; Y. Wang, Q.-Y. He and C.-M.Che, J.-F. Chiu, Proteomics, 6 (2006) 131; Y. Shi, W. Chu, Y. Wang, S.Wang, J. Du, J. Zhang, S. Li, G. Zhou, X. Qin and C. Zhang, Inorg. Chem.Comm., 30 (2013) 178; M. Monim-ul-Mehboob, M. Altaf, M. Fettouhi, A. A.Isab, M. I. M. Wazeer, M. N. Shaikh and S. Altuwaijri, Polyhedron, 61(2013) 225—each incorporated herein by reference in its entirety].

Lung and colorectal cancers are frequent causes of cancer-related deathin both males and females while cervix cancer is responsible for cancerdeaths in females exclusively. Hence, there remains an unmet, dire needof new drugs to treat such lethal diseases through chemotherapy.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect, the present disclosure provides a gold(I)complex having either of the following Formula 1 or Formula 2:

or a pharmaceutically acceptable salt, ester or prodrug thereof. R₁, R₂,R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁, R₁₂ and R₁₃ are each independentlya linear or branched, substituted or unsubstituted C₁-C₈ alkyl group ora substituted or unsubstituted C₆-C₈ aryl group. R₁₄ is a methyl groupor an ethyl group.

In one embodiment, R₁, R₂ and R₃ are each selected from the groupconsisting of a methyl group, an ethyl group, a propyl group, an n-butylgroup, an isobutyl group, a sec-butyl group, a tert-butyl group, ann-pentyl group, an isopropyl group, a neopentyl group, a sec-pentylgroup; a tert-pentyl group, an n-hexane group, an isohexane group and aneohexane group. R₄ and R₅ are each selected from the group consistingof a methyl group, an ethyl group, a phenyl group and a benzyl group.R₆, R₇, R₈ and R₉ are each selected from the group consisting of aphenyl group and a benzyl group. R₁₀, R₁₁, R₁₂ and R₁₃ are each selectedfrom the group consisting of a methyl group, an ethyl group, a phenylgroup and a benzyl group. R₁₄ is a methyl group or an ethyl group.

In one embodiment, the gold(I) complex has a formula selected from thegroup consisting of Formula 3, Formula 4, Formula 5 or Formula 6:

According to a second aspect, the present disclosure provides acomposition comprising the gold(I) complex in accordance with the firstaspect of the disclosure or a pharmaceutically acceptable salt, ester orprodrug thereof, and one or more pharmaceutically acceptable carriers.

In one embodiment, the pharmaceutical composition further comprises oneor more other active pharmaceutical agents.

In one embodiment, the pharmaceutical composition is in solid,semi-solid or liquid dosage forms.

In one embodiment, the pharmaceutical composition is formulated for oneor more modes of administration selected from the group consisting oforal administration, systemic administration, parenteral administration,inhalation spray, infusion, rectal administration, topicaladministration, intravesical administration, intradermal administration,transdermal administration, subcutaneous administration, intramuscularadministration, intralesional administration, intracranialadministration, intrapulmonal administration, intracardialadministration, intrasternal administration and sublingualadministration.

According to a third aspect, the present disclosure relates a method forinhibiting proliferation of cancer cells. The method comprisescontacting the cancer cells with the gold(I) complex according to thefirst aspect of the disclosure or a pharmaceutically acceptable salt,ester or prodrug thereof.

In one or more embodiments, the cancer cells contacted with the gold(I)complex are human cells.

In one embodiment, the cancer cells are at least one selected from thegroup consisting of lung cancer cells, colorectal cancer cells andcervical cancer cells.

In one embodiment, the gold(I) complex concentration is 5-50 μM.

In one embodiment, the gold(I) complex exhibits an IC₅₀ of 1-150 μM forinhibiting the proliferation and inducing the apoptosis of the cancercells.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1A illustrates the structure of mononuclear gold(I) precursorcompound for Complex (A1), [t-Bu₃PAuCl].

FIG. 1B illustrates the structure of binuclear gold(I) precursorcompound for Complexes (A2)-(A4), [(DPPM)(AuCl)₂].

FIG. 1C illustrates the structure of dithiocarbamate ligand for Complex(A2) NaS₂CN(CH₃)₂.

FIG. 1D illustrates the structure of dithiocarbamate ligand for Complex(A3), NaS₂CN(C₂H₅)₂.

FIG. 1E illustrates the structure of dithiocarbamate ligand forComplexes (A1) and (A4), NaS₂CN(C₇H₇)₂.

FIG. 2A shows the chemical structure of Complex (A1),[t-Bu₃PAuS₂CN(C₇H₇)₂].

FIG. 2B shows the chemical structure of Complex (A2),[(DPPM)Au₂(S₂CN(CH₃)₂)₂].

FIG. 2C shows the chemical structure of Complex (A3),[(DPPM)Au₂(S₂CN(C₂H₅)₂)₂].

FIG. 2D shows the chemical structure of Complex (A4),[(DPPM)Au₂(S₂CN(C₇H₇)₂)₂].

FIG. 3 is a graphic image showing the molecular structure of complex(A1) with atom labeling and displacement ellipsoids drawn at a 50%probability level.

FIG. 4 is a bar graph showing the concentration dependent in vitrocytotoxic effect of complexes (A1)-(A4) on the viability of HeLa cancercells.

FIG. 5 is a bar graph showing the concentration dependent in vitrocytotoxic effect of complexes (A1)-(A4) on the viability of HCT15 cancercells.

FIG. 6 is a bar graph showing the concentration dependent in vitrocytotoxic effect of complexes (A1)-(A4) on the viability of A549 cancercells.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure will now be described more fullyhereinafter with reference to the accompanying drawings, in which some,but not all embodiments of the disclosure are shown. Indeed, thesedisclosures may be embodied in many different forms and should not beconstrued as limited to the embodiments set forth herein; rather, theseembodiments are provided so that the present disclosure will satisfyapplicable legal requirements.

The present disclosure will be better understood with reference to thefollowing definitions:

Definitions

As used herein, “compound” and “complex” are intended to refer to achemical entity, whether in the solid, liquid or gaseous phase, andwhether in a crude mixture or purified and isolated.

The term “alkyl”, as used herein, unless otherwise specified, refers toa saturated straight, branched, or cyclic, primary, secondary, ortertiary hydrocarbon of typically C₁ to C₈, and specifically includesmethyl, trifluoromethyl, ethyl, propyl, isopropyl, cyclopropyl, butyl,isobutyl, 1-butyl, pentyl, cyclopentyl, isopentyl, neopentyl, hexyl,isohexyl, cyclohexyl, cyclohexylmethyl, 3-methylpentyl,2,2-dimethylbutyl, and 2,3-dimethylbutyl. The term optionally includessubstituted alkyl groups. Moieties with which the alkyl group can besubstituted are selected from the group consisting of hydroxyl, amino,alkylamino, aryl amino, alkoxy, aryloxy, nitro, cyano, sulfonic acid,sulfate, phosphonic acid, phosphate, or phosphonate, either unprotected,or protected as necessary, as known to those skilled in the art, forexample, as taught in Greene, et al., “Protective Groups in OrganicSynthesis”, John Wiley and Sons, Second Edition, 1991, herebyincorporated by reference in its entirety.

The term “aryl”, as used herein, and unless otherwise specified, refersto phenyl, biphenyl, or naphthyl, and preferably phenyl. The termincludes both substituted and unsubstituted moieties. The aryl group canbe substituted with one or more moieties selected from the groupconsisting of hydroxyl, amino, alkylamino, arylamino, alkoxy, aryloxy,nitro, cyano, sulfonic acid, sulfate, phosphonic acid, phosphate, orphosphonate, either unprotected, or protected as necessary, as known tothose skilled in the art, for example, as taught in Greene, et al.,“Protective Groups in Organic Synthesis”, John Wiley and Sons, SecondEdition, 1991, hereby incorporated by reference in its entirety.

As used herein, “analogue” refers to a chemical compound that isstructurally similar to a parent compound, but differs slightly incomposition (e.g., one atom or functional group is different, added, orremoved). The analogue may or may not have different chemical orphysical properties than the original compound and may or may not haveimproved biological and/or chemical activity. For example, the analoguemay be more hydrophilic or it may have altered reactivity as compared tothe parent compound. The analogue may mimic the chemical and/orbiologically activity of the parent compound (i.e., it may have similaror identical activity), or, in some cases, may have increased ordecreased activity. The analogue may be a naturally or non-naturallyoccurring variant of the original compound. Other types of analoguesinclude isomers (enantiomers, diastereomers, and the like) and othertypes of chiral variants of a compound, as well as structural isomers.

As used herein, “derivative” refers to a chemically or biologicallymodified version of a chemical compound that is structurally similar toa parent compound and (actually or theoretically) derivable from thatparent compound. A “derivative” differs from an “analogue” in that aparent compound may be the starting material to generate a “derivative,”whereas the parent compound may not necessarily be used as the startingmaterial to generate an “analogue.” A derivative may or may not havedifferent chemical or physical properties of the parent compound. Forexample, the derivative may be more hydrophilic or it may have alteredreactivity as compared to the parent compound. Derivatization (i.e.,modification) may involve substitution of one or more moieties withinthe molecule (e.g., a change in functional group). The term “derivative”also includes conjugates, and prodrugs of a parent compound (i.e.,chemically modified derivatives which can be converted into the originalcompound under physiological conditions).

The term “prodrug” refers to an agent that is converted into abiologically active form in vivo. Prodrugs are often useful because, insome situations, they may be easier to administer than the parentcompound. They may, for instance, be bioavailable by oral administrationwhereas the parent compound is not. The prodrug may also have improvedsolubility in pharmaceutical compositions over the parent drug. Aprodrug may be converted into the parent drug by various mechanisms,including enzymatic processes and metabolic hydrolysis [Harper, N. J.(1962). Drug Latentiation in Jucker, ed. Progress in Drug Research,4:221-294; Morozowich et al. (1977). Application of Physical OrganicPrinciples to Prodrug Design in E. B. Roche ed. Design ofBiopharmaceutical Properties through Prodrugs and Analogs, APhA; Acad.Pharm. Sci.; E. B. Roche, ed. (1977). Bioreversible Carriers in Drug inDrug Design, Theory and Application, APhA; H. Bundgaard, ed. (1985)Design of Prodrugs, Elsevier; Wang et al. (1999) Prodrug approaches tothe improved delivery of peptide drug, Curr. Pharm. Design.5(4):265-287; Pauletti et al. (1997). Improvement in peptidebioavailability: Peptidomimetics and Prodrug Strategies, Adv. Drug.Delivery Rev. 27:235-256; Mizen et al. (1998). The Use of Esters asProdrugs for Oral Delivery of β-Lactam antibiotics, Pharm. Biotech.11:345-365; Gaignault et al. (1996). Designing Prodrugs andBioprecursors I. Carrier Prodrugs, Pract. Med. Chem. 671-696; M.Asgharnejad (2000). Improving Oral Drug Transport Via Prodrugs, in G. L.Amidon, P. I. Lee and E. M. Topp, Eds., Transport Processes inPharmaceutical Systems, Marcell Dekker, p. 185-218; Balant et al. (1990)Prodrugs for the improvement of drug absorption via different routes ofadministration, Eur. Drug Metab. Pharmacokinet., 15(2): 143-53; Balimaneand Sinko (1999). Involvement of multiple transporters in the oralabsorption of nucleoside analogues, Adv. Drug Delivery Rev.,39(1-3):183-209; Browne (1997). Fosphenyloin (Cerebyx), Clin.Neuropharmacol. 20(1): 1-12; Bundgaard (1979). Bioreversiblederivatization of drugs—principle and applicability to improve thetherapeutic effects of drugs, Arch. Pharm. Chemi. 86(1): 1-39; H.Bundgaard, ed. (1985) Design of Prodrugs, New York: Elsevier; Fleisheret al. (1996). Improved oral drug delivery: solubility limitationsovercome by the use of prodrugs, Adv. Drug Delivery Rev. 19(2): 115-130;Fleisher et al. (1985). Design of prodrugs for improved gastrointestinalabsorption by intestinal enzyme targeting, Methods Enzymol. 112: 360-81;Farquhar D, et al. (1983). Biologically Reversible Phosphate-ProtectiveGroups, J. Pharm. Sci., 72(3): 324-325; Han, H. K. et al. (2000).Targeted prodrug design to optimize drug delivery, AAPS PharmSci., 2(1):E6; Sadzuka Y. (2000). Effective prodrug liposome and conversion toactive metabolite, Curr. Drug Metab., 1(1):31-48; D. M. Lambert (2000)Rationale and applications of lipids as prodrug carriers, Eur. J. Pharm.Sci., 11 Suppl 2:S15-27; Wang, W. et al. (1999) Prodrug approaches tothe improved delivery of peptide drugs. Curr Pharm. Des.,5(4):265-87—each incorporated herein by reference in its entirety]. Insome embodiments, “Pharmaceutically acceptable prodrugs” refer to acompound that is metabolized, for example hydrolyzed or oxidized, in thehost to form the pharmaceutical composition of the present disclosure.Typical examples of prodrugs include compounds that have biologicallylabile protecting groups on a functional moiety of the active compound.Prodrugs include compounds that can be oxidized, reduced, aminated,deaminated, hydroxylated, dehydroxylated, hydrolyzed, dehydrolyzed,alkylated, dealkylated, acylated, deacylated, phosphorylated,dephosphorylated to produce the active compound.

The term “therapeutically effective amount” as used herein refers tothat amount of the compound being administered which will relieve tosome extent one or more of the symptoms of the disorder being treated.In reference to cancer or pathologies related to increased celldivision, a therapeutically effective amount refers to that amount whichhas the effect of at least one of the following: (1) reducing the sizeof a tumor, (2) inhibiting (that is, slowing to some extent, preferablystopping) aberrant cell division, growth or proliferation, for examplecancer cell division, (3) preventing or reducing the metastasis ofcancer cells, (4) relieving to some extent (or, preferably, eliminating)one or more symptoms associated with a pathology related to or caused inpart by unregulated or aberrant cellular division, including forexample, cancer and (5) inducing apoptosis of cancer cells or tumorcells.

As used herein, the terms “therapies” and “therapy” can refer to anymethod(s), composition(s), and/or agent(s) that can be used in theprevention, treatment and/or management of a cancer or one or moresymptoms thereof.

As used herein, the terms “treat,” “treatment,” and “treating” in thecontext of the administration of a therapy to a subject in need thereofrefer to the reduction or inhibition of the progression and/or durationof cancer, the reduction or amelioration of the severity of cancer,and/or the amelioration of one or more symptoms thereof resulting fromthe administration of one or more therapies. In some embodiments, thesubject is a mammalian subject. In one embodiment, the subject is ahuman. “Treating” or “treatment” of a disease includes preventing thedisease from occurring in a subject that may be predisposed to thedisease but does not yet experience or exhibit symptoms of the disease(prophylactic treatment), inhibiting the disease (slowing or arrestingits development), providing relief from the symptoms or side-effects ofthe disease (including palliative treatment), and relieving the disease(causing regression of the disease). With regard to cancer orhyperplasia, these terms simply mean that the life expectancy of anindividual affected with a cancer will be increased or that one or moreof the symptoms of the disease will be reduced. In specific embodiments,such terms refer to one, two or three or more results following theadministration of one, two, three or more therapies: (1) astabilization, reduction or elimination of the cancer stem cellpopulation; (2) a stabilization, reduction or elimination in the cancercell population; (3) a stabilization or reduction in the growth of atumor or neoplasm; (4) an impairment in the formation of a tumor; (5)eradication, removal, or control of primary, regional and/or metastaticcancer; (6) a reduction in mortality; (7) an increase in disease-free,relapse-free, progression-free, and/or overall survival, duration, orrate; (8) an increase in the response rate, the durability of response,or number of patients who respond or are in remission; (9) a decrease inhospitalization rate, (10) a decrease in hospitalization lengths, (11)the size of the tumor is maintained and does not increase or increasesby less than 10%, preferably less than 5%, preferably less than 4%,preferably less than 2%, and (12) an increase in the number of patientsin remission. In certain embodiments, such terms refer to astabilization or reduction in the cancer stem cell population. In someembodiments, such terms refer to a stabilization or reduction in thegrowth of cancer cells. In some embodiments, such terms refer tostabilization or reduction in the cancer stem cell population and areduction in the cancer cell population. In some embodiments, such termsrefer to a stabilization or reduction in the growth and/or formation ofa tumor. In some embodiments, such terms refer to the eradication,removal, or control of primary, regional, or metastatic cancer (e.g.,the minimization or delay of the spread of cancer). In some embodiments,such terms refer to a reduction in mortality and/or an increase insurvival rate of a patient population. In further embodiments, suchterms refer to an increase in the response rate, the durability ofresponse, or number of patients who respond or are in remission. In someembodiments, such terms refer to a decrease in hospitalization rate of apatient population and/or a decrease in hospitalization length for apatient population.

“Pharmaceutically acceptable salt” or “pharmaceutically acceptableester” refers to a compound in a pharmaceutically acceptable form suchas an ester, a phosphate ester, a salt of an ester or a related) which,upon administration to a subject in need thereof, provides at least oneof the gold(I) complexes described herein. Pharmaceutically acceptablesalts and ester retain the biological effectiveness and properties ofthe free bases and which are obtained by reaction with inorganic ororganic acids such as hydrochloric acid, hydrobromic acid, sulfuricacid, nitric acid, phosphoric acid, methanesulfonic acid, ethanesulfonicacid, p-toluenesulfonic acid, salicylic acid, malic acid, maleic acid,succinic acid, tartaric acid, citric acid, and the like. Suitable saltsinclude those derived from alkali metals such as potassium and sodium,alkaline earth metals such as calcium and magnesium, among numerousother acids well known in the art.

A “pharmaceutical composition” refers to a mixture of the compoundsdescribed herein or pharmaceutically acceptable salts, esters orprodrugs thereof, with other chemical components, such asphysiologically acceptable carriers and excipients. One purpose of apharmaceutical composition is to facilitate administration of at leastone gold(I) complex to a subject.

As used herein, a “pharmaceutically acceptable carrier” refers to acarrier or diluent that does not cause significant irritation to anorganism and does not abrogate the biological activity and properties ofthe administered gold(I) complex. the term carrier encompasses anyexcipient, diluent, filler, salt, buffer, stabilizer, solubilizer,lipid, stabilizer, or other material well known in the art for use inpharmaceutical formulations. The choice of a carrier for use in acomposition will depend upon the intended route of administration forthe composition. The preparation of pharmaceutically acceptable carriersand formulations containing these materials is described in, e.g.,Remington's Pharmaceutical Sciences, 21st Edition, ed. University of theSciences in Philadelphia, Lippincott, Williams & Wilkins, PhiladelphiaPa., 2005, which is incorporated herein by reference in its entirety.Examples of physiologically acceptable carriers include buffers such asphosphate buffers, citrate buffer, and buffers with other organic acids;antioxidants including ascorbic acid; low molecular weight (less thanabout 10 residues) polypeptides; proteins, such as serum albumin,gelatin, or immunoglobulins; hydrophilic polymers such aspolyvinylpyrrolidone; amino acids such as glycine, glutamine,asparagine, arginine or lysine; monosaccharides, disaccharides, andother carbohydrates including glucose, mannose, or dextrins; chelatingagents such as EDTA; sugar alcohols such as mannitol or sorbitol;salt-forming counterions such as sodium; and/or nonionic surfactantssuch as TWEEN® (ICI, Inc.; Bridgewater, N.J.), polyethylene glycol(PEG), and PLURONICS™ (BASF; Florham Park, N.J.).

An “excipient” refers to an inert substance added to a pharmaceuticalcomposition to further facilitate administration of a compound.Examples, without limitation, of excipients include calcium carbonate,calcium phosphate, various sugars and types of starch, cellulosederivatives, gelatin, vegetable oils and polyethylene glycols.

The terms “including”, “such as”, “for example” and the like areintended to refer to exemplary embodiments and not to limit the scope ofthe present disclosure.

Gold(I) Complexes and Pharmaceutical Compositions Thereof

The present disclosure provides mono- and di-gold(I) complexes havingmedicinal or pharmaceutical properties, preferably antitumor oranticancer properties. In these monomeric or binuclear gold(I)complexes, each gold(I) atom is coordinated, preferably chelated by twoor more mixed ligands that are based on phosphine or dithiocarbamatefunctional groups as shown below:

The phosphine-based ligand can be either monodentate (i.e. monophosphineand having one P donor atom) or bidentate (i.e. bisphosphine and havingtwo P donor atoms) and include derivatives thereof. The bisphosphineligand further includes a bridging short alkyl group between thephosphorus atoms, for example, a methyl or an ethyl group.

The dithiocarbamate-based ligand, on the other hand, coordinates orchelates a gold(I) atom in a monodentate manner. The nitrogen atom of adithiocarbamate-based ligand can be substituted with one or more alkylor aryl groups, for example, substituted or unsubstituted C₁-C₈ alkylgroups or substituted or unsubstituted C₆-C₈ aryl groups.

Hence, a phosphine gold(I) dithiocarbamate complex provided by thepresent disclosure has a generic formula of either Formula 1 or Formula2:

where:

the complex is either mononuclear or binuclear having one or two goldatoms;

each of the gold atoms is coordinated with one P donor atom from aphosphine-based ligand and one S donor atom from a dithiocarbamate-basedligand;

R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁, R₁₂ and R₁₃ are eachindependently a linear or branched, substituted or unsubstituted C₁-C₈alkyl group or a substituted or unsubstituted C₆-C₈ aryl group; and

R₁₄ is a methyl group or an ethyl group.

A monomeric phosphine gold(I) dithiocarbamate complex contains oneS—Au—P motif whereas a dimeric phosphine gold(I) dithiocarbamate complexcontains two of the structural motifs. The Au—S and Au—P bond distancesare equal or nearly equal to each other at 1.8-2.8 Å, preferably 1.8-2.5Å, more preferably 1.8-2.3 Å, even more preferably 2-2.3 Å.

In some embodiments, a phosphine gold(I) dithiocarbamate complex inaccordance with the present disclosure has a generic formula of eitherFormula 1 or Formula 2. The complex is either mononuclear or binuclearhaving one or two gold atoms. Each of the gold atoms is coordinated withone P donor atom from a phosphine-based ligand and one S donor atom froma dithiocarbamate-based ligand, where:

R₁, R₂ and R₃ are each selected from the group consisting of a methylgroup, an ethyl group, a propyl group, an n-butyl group, an isobutylgroup, a sec-butyl group, a tert-butyl group, an n-pentyl group, anisopropyl group, a neopentyl group, a sec-pentyl group; a tert-pentylgroup, an n-hexane group, an isohexane group and a neohexane group;

R₄ and R₅ are each selected from the group consisting of a methyl group,an ethyl group, a phenyl group and a benzyl group; R₆, R₇, R₈ and R₉ areeach selected from the group consisting of a phenyl group and a benzylgroup;

R₁₀, R₁₁, R₁₂ and R₁₃ are each selected from the group consisting of amethyl group, an ethyl group, a phenyl group and a benzyl group; and

R₁₄ is a methyl group or an ethyl group.

In one embodiment, a phosphine gold(I) dithiocarbamate complex of thepresent disclosure is according to one of the following Formulas 3-6:

In this embodiment, the phosphine gold(I) dithiocarbamate complex is oneof the following:

-   tri-tert-butyl-phosphine gold(I) dibenzyldithiocarbamate (Formula    5),-   1,1-bis(diphenylphosphino)methane digold(I) dimethyldithiocarbamate    (Formula 6),-   1,1-bis(diphenylphosphino)methane digold(I) diethyldithiocarbamate    (Formula 7), and-   1,1-bis(diphenylphosphino)methane digold(I) dibenzyldithiocarbamate    (Formula 8).

In certain embodiments, especially but not limited to pharmaceuticalapplications, the phosphine gold(I) dithiocarbamate complex can furtherinclude a counter-anion to form a pharmaceutically acceptable salt. Asused herein, the term “counter-anion” refers to an anion, preferably apharmaceutically acceptable anion that is associated with a positivelycharged mononuclear or binuclear phosphine gold(I) dithiocarbamatecomplex of at least one of the Formulas 3-8. Non-limiting examples ofcounter-anions include halides such as fluoride, chloride, bromide,iodide; nitrate; sulfate; phosphate; methanesulfonate; ethanesulfonate;p-toluenesulfonate, salicylate, malate, maleate, succinate, tartarate;citrate; acetate; perchlorate; trifluoromethanesulfonate (triflate);acetylacetonate; hexafluorophosphate; and hexafluoroacetylacetonate. Insome embodiments, the counter-anion is a halide, preferably chloride.

Another aspect of the present disclosure relates to pharmaceuticalcomposition comprising one or more of the phosphine gold(I)dithiocarbamate complexes described herein. In other words, the gold(I)complexes described herein or analogues or derivatives thereof can beprovided in a pharmaceutical composition. Depending on the intended modeof administration, the pharmaceutical composition can be in the form ofsolid, semi-solid or liquid dosage forms, such as, for example, tablets,suppositories, pills, capsules, powders, liquids, or suspensions,preferably in unit dosage form suitable for single administration of aprecise dosage. The compositions will include a therapeuticallyeffective amount of one or more of the gold(I) complexes describedherein or derivatives thereof in combination with a pharmaceuticallyacceptable carrier and, in addition, may include other medicinal agents,pharmaceutical agents, carriers, diluents or other non-activeingredients. By pharmaceutically acceptable is meant a material that isnot biologically or otherwise undesirable, which can be administered toan individual along with the selected compound without causingsignificant unacceptable biological effects or interacting in adeleterious manner with the other components of the pharmaceuticalcomposition in which it is contained.

A phosphine gold(I) dithiocarbamate complex or an analogue or derivativethereof may be used in conjunction with one or more additionalcompounds, in the treatment or prevention of neoplasm; of tumor orcancer cell division, growth, proliferation and/or metastasis in amammalian subject; inhibition of thioredoxin reductase (TrxR) activityin tumor and/or cancer cells; induction of death or apoptosis of tumorand/or cancer cells; and/or any other form of proliferative disorder. Agold(I) complex of the present disclosure can be formulated as apharmaceutical composition.

It has been reported that thiol/selenol containing proteins, likethioredoxin reductase (TrxR), are the major targets for gold(I) basedanticancer agents. An accepted mechanism of action is that phosphinegold(I) complexes act as irreversible inhibitors of at least themammalian mitochondrial thioredoxin reductase (TrxR2), whose expressionis elevated in cancer cells, thereby leading to the eventual death ofthe cancer cells [J. C. Lima and L. Rodriguez, J. Med. Chem., 11 (2011)921; S. Urig, K. Fritz-Wolf, R. Réau, C. Herold-Mende, K. Tóth, E.Davioud-Charvet and K. Becker, Angew. Chem. Int. Ed. 45 (2006) 1881; V.Gandin, A. P. Fernandes, M. P. Rigobello, B. Dani, F. Sorrentino, F.Tisato, M. Bjornstedt, A. Bindoli, A. Sturaro, R. Relia and C. Marzano,Biochem Pharmacol 79 (2010) 90; Omata, Yo; Folan, Matt; Shaw, Melissa;Messer, Regina L.; Lockwood, Petra E.; Hobbs, David; Bouillaguet, Serge;Sano, Hidehiko; Lewis, Jill B.; Wataha, John C, Toxicology in vitro 20(2006) 882—each incorporated herein by reference in its entirety]. OtherTrx reductases that may also be inhibited by phosphine gold(I) complexesare cytosolic Trx reductase (TrxR1), testis specific TrxR3,glutathione-disulfide reductase (GSR) and trypanothione reductase.

The neoplastic activity of the tumor or cancer cells may be localized orinitiated in one or more of the following: blood, brain, bladder, lung,cervix, ovary, colon, rectum, pancreas, skin, prostate gland, stomach,breast, liver, spleen, kidney, head, neck, testicle, bone (includingbone marrow), thyroid gland, central nervous system. The phosphinegold(I) dithiocarbamate complex of the present disclosure or thepharmaceutical composition thereof is especially effective in thetreatment or prevention of colorectal cancer (including colon cancer,rectum cancer and bowel cancer); lung cancer (including non-small celllung carcinoma or NSCLC and small cell lung carcinoma); cervical cancer(including the histologic subtypes of squamous cell carcinoma,adenocarcinoma, adenosquamous carcinoma, small cell carcinoma,neuroendocrine tumor, glass cell carcinoma, villoglandularadenocarcinoma, melanoma and lymphoma).

A pharmaceutical composition comprising one or more gold(I) complexes ofthe present disclosure can then be administered orally, systemically,parenterally, by inhalation spray, rectally, or topically in dosage unitformulations containing conventional nontoxic pharmaceuticallyacceptable carriers, adjuvants, and vehicles as desired. In someembodiments, the method of administration of the steroid or an analogueor derivative thereof is oral. In other embodiments, the compound or ananalogue or derivative thereof is administered by injection, such as,for example, through a peritumoral injection.

Topical administration can also involve the use of transdermaladministration such as transdermal patches or iontophoresis devices. Theterm parenteral as used herein includes intravesical, intradermal,transdermal, subcutaneous, intramuscular, intralesional, intracranial,intrapulmonal, intracardial, intrasternal and sublingual injections, orinfusion techniques. Formulation of drugs is discussed in, for example,Hoover, John E., Remington's Pharmaceutical Sciences, Mack PublishingCo., Easton, Pa.; 1975. Another example of includes Liberman, H. A. andLachman. L., Eds., Pharmaceutical Dosage Forms, Marcel Decker, New York,N.Y., 1980, which is incorporated herein by reference in its entirety.

Injectable preparations, for example, sterile injectable aqueous oroleaginous suspensions can be formulated according to the known artusing suitable dispersing or wetting agents and suspending agents. Thesterile injectable preparation can also be a sterile injectable solutionor suspension in a nontoxic parenterally acceptable diluent or solvent,for example, as a solution in 1,3-butanediol. Among the acceptablevehicles and solvents that can be employed are water, Ringer's solution,and isotonic sodium chloride solution. In addition, sterile, fixed oilsare conventionally employed as a solvent or suspending medium. For thispurpose any bland fixed oil can be employed including synthetic mono- ordiglycerides. In addition, fatty acids such as oleic acid find use inthe preparation of injectables. Dimethyl acetamide, surfactantsincluding ionic and non-ionic detergents, polyethylene glycols can beused. Mixtures of solvents and wetting agents such as those discussedabove are also useful. Suppositories for rectal administration of thecompound or an analogue or derivative thereof can be prepared by mixingthe steroid or an analogue or derivative thereof with a suitablenonirritating excipient such as cocoa butter, synthetic mono- di- ortriglycerides, fatty acids and polyethylene glycols that are solid atordinary temperatures but liquid at the rectal temperature and willtherefore melt in the rectum and release the drug.

Solid dosage forms for oral administration can include capsules,tablets, pills, powders, and granules. In such solid dosage forms, thecompounds of this disclosure are ordinarily combined with one or moreadjuvants appropriate to the indicated route of administration. Ifadministered per os, a contemplated steroid or an analogue or derivativethereof can be admixed with lactose, sucrose, starch powder, celluloseesters of alkanoic acids, cellulose alkyl esters, talc, stearic acid,magnesium stearate, magnesium oxide, sodium and calcium salts ofphosphoric and sulfuric acids, gelatin, acacia gum, sodium alginate,polyvinylpyrrolidone, and/or polyvinyl alcohol, and then tableted orencapsulated for convenient administration. Such capsules or tablets cancontain a controlled-release formulation as can be provided in adispersion of active compound in hydroxypropylmethyl cellulose. In thecase of capsules, tablets, and pills, the dosage forms can also comprisebuffering agents such as sodium citrate, magnesium or calcium carbonateor bicarbonate. Tablets and pills can additionally be prepared withenteric coatings.

For therapeutic purposes, formulations for parenteral administration canbe in the form of aqueous or non-aqueous isotonic sterile injectionsolutions or suspensions. These solutions and suspensions can beprepared from sterile powders or granules having one or more of thecarriers or diluents mentioned for use in the formulations for oraladministration. A contemplated steroid or an analogue or derivativethereof of the present disclosure can be dissolved in water,polyethylene glycol, propylene glycol, ethanol, corn oil, cottonseedoil, peanut oil, sesame oil, benzyl alcohol, sodium chloride, and/orvarious buffers. Other adjuvants and modes of administration are welland widely known in the pharmaceutical art.

Liquid dosage forms for oral administration can include pharmaceuticallyacceptable emulsions, solutions, suspensions, syrups, and elixirscontaining inert diluents commonly used in the art, such as water. Suchcompositions can also comprise adjuvants, such as wetting agents,emulsifying and suspending agents, and sweetening, flavoring, andperfuming agents.

The amount of active ingredient that can be combined with the carriermaterials to produce a single dosage form varies depending upon themammalian subject treated and the particular mode of administration.

Methods of Synthesis

The mono- and di-gold(I) complexes having mixed phosphine-based anddithiocarbamate-based ligands as described herein are not limited bytheir synthesis routes and methods. The gold(I) complexes with ligandshaving dithiocarbamate and phosphine functionalities can be prepared bypreviously reported synthesis and methods with slight modifications asrecognized as appropriate by a person of ordinary skill in thepharmaceutical or medicinal chemistry art [U.S. Pat. Appl. Pub.US2014/0142065A1; F. K. Keter, I. A. Guzei, M. Nell; W. E. van Zyl andJ. Darkwa, Inorg. Chem, 53 (2014) 2058; C. Li, “Gold(I) and Gold(III)Phosphine Complexes Exhibiting Weak Au^(I) . . . Au^(I) Interactions andUnsupported Au^(II)—Au^(II) Bonds—Synthesis, Spectroscopy, Host-GuestChemistry and Reactivity Studies”, A thesis submitted in partialfulfillment of the requirements for the Degree of Doctor of Philosophyat The University of Hong Kong (2002) 1; P. Tadbuppa, “Phosphinegold(I)thiolates: Synthesis and Biological Activities”, A thesis submitted forthe degree of Doctor of Philosophy at the National University ofSingapore (2009) 1—each incorporated herein by reference in itsentirety].

In one embodiment, the gold(I) complexes of the present disclosure areprepared using monomeric or dimeric phosphinegold(I) precursor compoundsand dialkyl- or diaryldithiocarbamate sodium or potassium anhydrous orhydrated salts. With the gold(I) precursor compounds, a monomericgold(I) precursor compound bears a monophosphine monodentate ligand anda halide ligand while a dimeric gold(I) precursor compound carries abisphosphine bisdentate ligand and two halide ligands. The gold(I)precursor compound and the dithiocarbamate salt are mixed in an organicsolvent such as ethanol or acetone at room temperature and the reactionmixture is continuously stirred for 2-4 h. The obtained solution at theend of the stirring is pale/light yellow and is either clear or turbid.The turbidity can be removed by addition of a few drops up to 5 mL ofwater (preferably distilled and deionized). The solution is filtered andleft to crystallize by slow evaporation at room temperature. Colorlessor yellow crystal or semi-crystalline products are obtained after 3-7days.

Method of Inhibiting Proliferation of Cancer Cells and Inducing CancerCell Death

The present disclosure further provides a method of inhibitingproliferation of human cancer cells and inducing apoptosis of the humancancer cells in vitro or in vivo. Human cancer cells are contacted with1-100 μM of a gold(I) complex in accordance with the present disclosureor a composition comprising the gold(I) complex at the definedconcentration range, preferably 2-75 μM, more preferably 5-50 μM, evenmore preferably 5-10 μM, 10-25 μM, 5-25 μM, 25-50 μM and 10-50 μM. Theviability of cells can be determined by standard cell viability assayssuch as but not limited to ATP test, Calcein AM assay, clonogenic assay,ethidium homodimer assay, Evans blue assay, Fluorescein diacetatehydrolysis/propidium iodide staining assay, flow cytometry assay,formazan-based assays (MTT.XTT), green fluorescent protein assay,lactate dehydrogenase assay, methyl vilet assay, propidium iodide assay,Resazurin assay, Trypan Blue assay and TUNEL, assay.

When contacted with the gold(I) complex at the defined concentration,the viability of the human cancer cells is reduced to at least 95%,preferably at least 85%, more preferably at least 75%, even morepreferably at least 50%, at least 45%, at least 40%, at least 35%, atleast 30%, at least 25%, at least 20%, most preferably at least 15%, atleast 12.5%, at least 10%, at least 7.5%, at least 5%, at least 2.5%, atleast 2%, at least 1% and at least 0.5%.

The half maximal inhibitory concentration (IC₅₀) values of the gold(I)complexes against the human cancer cells are no higher than 150 μM,preferably at least no higher than 100 μM, more preferably no higherthan 50 μM, no higher than 30 μM, even more preferably no higher than 15μM, no higher than 12 μM, most preferably no higher than 10 μM, nohigher than 5 μM and no higher than 2 μM. In some embodiments, comparedto cisplatin, the IC₅₀ values of the gold(I) complexes provided hereinare at least 2 times lower, preferably 2 to 15 times lower, morepreferably 3 to 15 times lower, even more preferably 5 to 15 timeslower.

In some embodiments, the human cancer cells are derived from commercialcell line models, including but are not limited to HeLa cervical cancercells, A549 lung cancer cells, HCT-15 colon cancer cells, HCT-8 or HRT-8colon cancer cells, DLD-1 colon cancer cells, MCF-7 breast cancer cells,A2780 ovarian cancer cells, A2780-cis cisplatin-resistant ovarian cancercells, PC-3 prostatic cancer cells, DU-145 prostatic cancer cells,SGC7907 gastrointestinal cancer cells.

In other embodiments, the human cancer cells are cancer cells of a humanpatient who has been diagnosed with, is suspected of having, or issusceptible to or at risk of having at least one form of cancer,preferably colorectal cancer, cervical cancer and/or lung cancer.

Methods of Treating Cancers and Combination Therapies

Cancers such as but not limited to sarcomas, carcinomas, melanomas,myelomas, gliomas and lymphomas can be treated or prevented with thegold(I) complexes provided herein. In some embodiments, methodsincorporating the use of at least one of the gold(I) complexes of thepresent disclosure are effective in the treatment or prevention ofcancer of the blood, brain, bladder, lung, cervix, ovary, colon, rectum,pancreas, skin, prostate gland, stomach, breast, liver, spleen, kidney,head, neck, testicle, bone (including bone marrow), thyroid gland orcentral nervous system. In some embodiments, these methods areespecially effective in the treatment or prevention of cervical, colonand lung cancers.

The methods for treating cancer and other proliferative disordersdescribed herein inhibit, remove, eradicate, reduce, regress, diminish,arrest or stabilize a cancerous tumor, including at least one of thetumor growth, tumor cell viability, tumor cell division andproliferation, tumor metabolism, blood flow to the tumor and metastasisof the tumor. In some embodiments, after treatment with one or moregold(I) complexes or a pharmaceutical composition thereof, the size of atumor, whether by volume, weight or diameter, is reduced by at least 5%,10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%,99% or 100%, relative to the tumor size before treatment. In otherembodiments, after treatment with the one or more gold(I) complexes of apharmaceutical composition thereof, the size of a tumor does not reducebut is maintained the same as the tumor size before treatment. Methodsof assessing tumor size include but are not limited to CT Scan, MRI,DCE-MRI and PET Scan.

In some embodiments, the method for treating cancer and otherproliferative disorders involves the administration of a unit dosage ora therapeutically effective amount of one or more of gold(I) complexesor a pharmaceutical composition thereof to a mammalian subject(preferably a human subject) in need thereof. As used herein, “a subjectin need thereof” refers to a mammalian subject, preferably a humansubject, who has been diagnosed with, is suspected of having, issusceptible to, is genetically predisposed to or is at risk of having atleast one form of cancer. Routes or modes of administration are as setforth herein. The dosage and treatment duration are dependent on factorssuch as bioavailability of a drug, administration mode, toxicity of adrug, gender, age, lifestyle, body weight, the use of other drugs anddietary supplements, cancer stage, tolerance and resistance of the bodyto the administered drug, etc., then determined and adjustedaccordingly. The one or more of gold(I) complexes or a pharmaceuticalcomposition thereof may be administered in a single dose or multipleindividual divided doses. In some embodiments, the interval of timebetween the administration of gold(I) complexes or a pharmaceuticalcomposition thereof and the administration of one or more additionaltherapies may be about 1-5 minutes, 1-30 minutes, 30 minutes to 60minutes, 1 hour, 1-2 hours, 2-6 hours, 2-12 hours, 12-24 hours, 1-2days, 2 days, 3 days, 4 days, 5 days, 6 days, 7 days, 1 week, 2 weeks, 3weeks, 4 weeks, 5 weeks, 6 weeks, 7 weeks, 8 weeks, 9 weeks, 10 weeks,15 weeks, 20 weeks, 26 weeks, 52 weeks, 11-15 weeks, 15-20 weeks, 20-30weeks, 30-40 weeks, 40-50 weeks, 1 month, 2 months, 3 months, 4 months 5months, 6 months, 7 months, 8 months, 9 months, 10 months, 11 months, 12months, 1 year, 2 years, or any period of time in between. In certainembodiments, dinuclear gold(I) compounds and one or more additionaltherapies are administered less than 1 day, 1 week, 2 weeks, 3 weeks, 4weeks, one month, 2 months, 3 months, 6 months, 1 year, 2 years, or 5years apart.

In certain embodiments, a gold(I) complex of the present disclosure or apharmaceutical composition thereof may be used in combination with oneor more other antineoplastic or chemotherapeutic agents. A non-limitinglist of examples of chemotherapeutic agents are aflibercept,asparaginase, bleomycin, busulfan, carmustine, chlorambucil, cladribine,cyclophosphamide, cytarabine, dacarbazine, daunorubicin, doxorubicin,etoposide, fludarabine, gemcitabine, hydroxyurea, idarubicin,ifosfamide, irinotecan, lomustine, mechlorethamine, melphalan,mercaptopurine, methotrexate, mitomycin, mitoxantrone, pentostatin,procarbazine, 6-thioguanine, topotecan, vinblastine, vincristine,retinoic acid, oxaliplatin, cis-platin, carboplatin, 5-FU(5-fluorouracil), teniposide, amasacrine, docetaxel, paclitaxel,vinorelbine, bortezomib, clofarabine, capecitabine, actinomycin D,epirubicine, vindesine, methotrexate, tioguanine (6-thioguanine),tipifarnib. Examples for antineoplastic agents which are protein kinaseinhibitors include imatinib, erlotinib, sorafenib, sunitinib, dasatinib,nilotinib, lapatinib, gefitinib, temsirolimus, everolimus, rapamycine,bosutinib, pzopanib, axitinib, neratinib, vatalanib, pazopanib,midostaurin and enzastaurin. Examples for antineoplastic agents whichare antibodies comprise trastuzumab, cetuximab, panitumumab, rituximab,bevacizumab, mapatumumab, conatumumab, lexatumumab and the like.

EXAMPLES

The following examples are provided is illustrations of the disclosureand to provide those of ordinary skill in the art with specificpreferred methods of synthesizing and characterizing gold(I) complexeswithin the scope of the present disclosure, and are not intended tolimit the scope of what the applicants regard as their disclosure andthe scope of the appended claims.

Example 1 Materials and Methods

Chemicals and solvents used in the synthesis were of analytical gradeand were used without further purification. All the reactions werecarried under normal ambient conditions. All chemicals were obtainedfrom Sigma-Aldrich St. Louis, Mo. United States and Strem Chemicals,Massachusetts, United States.

Elemental analyses were performed on Perkin Elmer Series 11 (CHNS/O),Analyzer 2400. The solid state FTIR spectra of free ligands and theircorresponding gold(I) complexes were recorded on a Perkin-Elmer FTIR 180spectrophotometer or NICOLET 6700 FTIR using KBr pellets over the range4000-400 cm⁻¹.

¹H, ¹³C and ³¹P NMR spectra were recorded on a LAMBDA 500spectrophotometer operating at 500.01, 125.65 and 200.0 MHzrespectively; corresponding to a magnetic field of 11.74 T.Tetramethylsilane (TMS) was used as an internal standard for ¹H and ¹³CNMR measurements. Triphenylphosphine (TPP) was used as an externalstandard for ³¹P NMR measurement.

The ¹³C NMR spectra were obtained with ¹H broadband decoupling. Thespectral conditions were: 32 k data points, 0.967 s acquisition time,1.00 s pulse delay and 45° pulse angle. The structure of the gold(I)precursor compound is shown in FIG. 1A while structures of the freeligands used in this disclosure are as shown in FIGS. 1B-1E. The ¹H, ¹³Cand ³¹P NMR chemical shifts of metal precursors and free ligands aregiven in Tables 1 and 2. The chemical structures of the synthesizedcomplexes (A1-A4) are given in FIGS. 2A-2D.

TABLE 1 Solution ¹H NMR chemical shifts (ppm) of the free gold(I) metalprecursors and free ligand molecules. Compound H—(CH₃) H—(CH₂) H—(Ph)[t-Bu₃PAuCl] 1.52 — — NaS₂CN(CH₃)₂•H₂O 3.55 — — NaS₂CN(C₂H₅)₂•3H₂O 1.234.03 — NaS₂CN(C₇H₇)₂•xH₂O — 4.98 7.01-7.22 [(DPPM)(AuCl)₂] — 2.497.39-7.76

TABLE 2 Solution ¹C and ³¹P NMR chemical shifts (ppm) of the freegold(I) metal precursors and free ligand molecules. Compound C—(CH₃)C—(CH₂) C—(Ph) C(C—P) C(C═S) ³¹P [t-Bu₃PAuCl] 32.23 — — 39.42 — −6.00NaS₂CN(CH₃)₂•H₂O 45.12 — — — 212.82 — NaS₂CN(C₂H₅)₂•3H₂O 12.31 49.61 — —206.7 — NaS₂CN(C₇H₇)₂•H₂O 56.9 — 127-137 — 213.53 — [(DPPM)(AuCl)₂] —24.60 128-133 — — 40.20

Example 2 Synthesis of Complex (A1), [t-Bu₃PAuS₂CN(C₇H₇)₂]

[t-Bu₃PAuCl] (0.217 g, 0.05 mmol) in 10 mL of dichloromethane was addedin sodium dibenzyldithiocarbamate (0.136 g, 0.05 mmol) in 15 mL ofethanol at room temperature. Upon continuous stirring the reactionmixture for 3 h, the transparent light yellow solution was obtained,filtered to avoid any impurity and kept undisturbed for crystallizationby slow evaporation at room temperature. The colorless block likecrystals was obtained after seven days. A suitable quality crystal waschosen for X-ray diffraction analysis. Yield: 0.312 g, (93%). Anal.Calc. for C₂₇H₄₁AuNPS₂: C, 48.28; H, 6.15; N, 2.09; S, 9.54; Found: C,48.17; H, 6.33; N, 2.02; S, 9.43. IR cm⁻¹: 3035 (w), 2995 (m), 2905 (m),1491 (s), 1456 (s), 1378 (m), 1213 (s), 1170 (m), 1022 (m), 972 (s), 806(m), 521 (s), 478 (m). NMR (CDCl₃-d₁): ¹H, δ 1.57 (27H, C(2)H), 5.17(4H, C(4)H), 7.32-7.34 (20H, H(Ph)); ¹³C, δ 32.29C(2), 39.40C(1),55.79C(4), 127.35-136.30C(Ph), and 210.15C(3); ³¹P: δ −7.83.

Example 3 Synthesis of Complex (A2), [(DPPM)Au₂(S₂CN(CH₃)₂)₂]

[μ-Bis(diphenylphosphino)methane]dichlorodigold(I), [(DPPM)(AuCl)₂](0.425 g, 0.05 mmol) in 10 mL CH₂Cl₂ was added in Sodiumdimethyldithiocarbamate monohydrate (0.144 g, 0.10 mmol) in 15 mL C₂H₅OHat room temperature. Upon continuous stirring the reaction mixture for 3h, the transparent yellow solution was obtained, filtered to avoid anyimpurity and kept undisturbed for crystallization by slow evaporation atroom temperature. The yellow very small crystals were obtained afterfive days. Anal. Calc. for C₃₁H₃₄Au₂N₂P₂S₄: C, 36.55; H, 3.36; N, 2.75;S, 12.59; Found: C, 36.45; H, 3.53; N, 2.87; S, 12.68. Yield: 0.397 g,(78%). IR cm⁻¹: 3038 (w), 2980 (w), 2917 (w), 1481 (m), 1432 (s), 1370(m), 1270 (m), 1147 (w), 1099 (m), 970 (m), 918 (w), 550 (s), 479 (m).NMR (DMSO-d₆): ¹H, δ 2.49 (2H, C(1)H), 4.47 (12H, C(3)H), 7.31-7.79(20H, H(Ph)); ¹³C, δ 30.68C(1), 44.76C(3), 128.78-133.25C(Ph), and208.15C(2); ³¹P: δ 39.66.

Example 4 Synthesis of Complex (A3), [(DPPM)Au₂(S₂CN(C₂H₅)₂)₂]

[μ-Bis(diphenylphosphino)methane]dichlorodigold(I), [(DPPM)(AuCl)₂](0.425 g, 0.05 mmol) in 10 mL CH₂Cl₂ was added in Sodiumdiethyldithiocarbamatetrihydrate (0.226 g, 0.10 mmol) in 15 mL of C₂H₅OHat room temperature. Upon continuous stirring the reaction mixture for 3h, the transparent yellow solution was obtained on the addition of 3 mLwater was for clarity, filtered to avoid any impurity and keptundisturbed for slow evaporation at room temperature. After three daysyellow semi-crystalline product was obtained. Anal. Calc. forC₃₅H₄₂Au₂N₂P₂S₄: C, 39.11; H, 3.94; N, 2.61; S, 11.93; Found: C, 39.05;H, 3.83; N, 2.57; S, 11.68. Yield: 0.392 g, (73%). IR cm⁻¹: 3043 (w),2970 (w), 2921 (w), 1486 (m), 1432 (s), 1374 (m), 1265 (m), 1137 (w),1087 (m), 982 (m), 908 (w), 560 (s), 478 (m). NMR (DMSO-d₆): ¹H, δ 1.22(12H, C(4)H), 2.49 (2H, C(1)H), 4.49 (8H, C(3)H), 7.33-7.79 (20H,H(Ph)); ¹³C, δ 12.17C(4), 30.66C(1), 49.06C(3), 128.83-133.29C(Ph), and206.62C(2); ³¹P: δ 40.69.

Example 5 Synthesis of Complex (A4), [(DPPM)Au₂(S₂CN(C₇H₇)₂)₂]

[μ-Bis(diphenylphosphino)methane]dichlorodigold(I), [(DPPM)(AuCl)₂](0.425 g, 0.05 mmol) in 10 mL CH₂Cl₂ was added in sodiumdiebenzyldithiocarbamatetrihydrate (0.272 g, 0.10 mmol) in 15 mL ofC₂H₅OH at room temperature. Upon continuous stirring the reactionmixture for 3 h, a turbid solution was obtained initially. Thetransparent pale yellow solution was obtained on addition of 3 mL ofwater for the removal of turbidity, filtered to avoid any impurity andkept in dark for slow evaporation. The bright yellow crystalline productwas obtained after seven days. Anal. Calc. for C₅₅H₅₀Au₂N₂P₂S₄: C,49.93; H, 3.81; N, 2.12; S, 9.69; Found: C, 49.85; H, 3.85; N, 2.15; S,9.58. Yield: 0.549 g, (83%), IR cm⁻¹: 3025 (w), 2919 (w), 1489 (s), 1432(s), 1351 (m), 1209 (s), 1147 (m), 1025 (m), 970 (s), 810 (w), 518 (m),479 (m). NMR (DMSO-d₆): ¹H, δ 2.49 (2H, C(1)H), 5.00 (8H, C(3)H),7.23-7.83 (40H, H(Ph)); ¹³C, δ 30.99C(1), 56.10C(3), 126.88-135.96C(Ph),and 208.54C(2); ³¹P: δ 40.20.

Example 6 Stability of Synthesized Gold(I) Complexes

Complexes (A1) and (A2) were dissolved in DMSO-d₆ and analyzed by ¹H and¹³C {1H} NMR measurements. The extent of decomposition over time wasdetermined by comparing the NMR spectra collected after 1, 6, 12, 24, 48and 72 h. No significant change in the chemical shifts and the splittingpatterns of compounds (A1) and (A2) was observed in their time dependent¹H NMR spectra.

Additionally, Complexes (A1)-(A4) were found to be completely soluble inpolar organic solvents i.e. DMSO and DMF; and sparingly soluble inwater.

Example 7 X-Ray Diffraction Studies of Synthesized Gold(I) Complexes

Pale yellow plate-like crystals of Complex (A1) were obtained byrecrystallization of the final product using a mixture of solvents i.e.C₂H₅OH and H₂O in 4:1 v/v ratio under slow evaporation at roomtemperature. The intensity data were collected at 173K (−100° C.) on aStoe Mark II-Image Plate Diffraction System equipped with a two-circlegoniometer using MoKα graphite mono chromated radiation (λ=0.71073 Å)[Stoe & Cie, X-Area & X-RED32, GmbH, Darmstadt, Germany,(2009)—incorporated herein by reference in its entirety]. The structurewas solved by direct methods with SHELXS-97. The refinement and allfurther calculations were carried out with SHELXL-2013 [G. M. Sheldrick,Acta Cryst., A64 (2008) 112—incorporated herein by reference in itsentirety]. The C-bound H-atoms were included in the calculated positionsand treated as riding atoms: C—H=0.95, 0.99 and 0.98 Å for CH(aromatic), CH₂ and CH₃, respectively, withU_(iso)(H)=1.5U_(eq)(C-methyl) and =1.2U_(eq) (C) for other H-atoms. Thenon-H atoms were refined anisotropically, using weighted full-matrixleast-squares on F². A semi-empirical absorption correction was appliedusing the MULscanABS routine in PLATON [A. L. Spek, Acta Cryst., D65(2009) 148—incorporated herein by reference in its entirety]. FIG. 3,which is generated using the program MERCURY, is a graphic image showingthe molecular structure of complex (A1) with atom labeling anddisplacement ellipsoids drawn at a 50% probability level [C. F. Macrae,I. J. Bruno, J. A. Chisholm, P. R. Edgington, P. McCabe, E. Pidcock, L.Rodriguez-Monge, R. Taylor, J. van de Streek and P. A. Wood, J. Appl.Cryst., 41 (2008) 466—incorporated herein by reference in its entirety].A summary of crystal data and refinement details for gold(I) complex(A1) are given in Table 3. Selected bond lengths and bond angles aregiven in Table 4.

In the X-ray structure of Complex (A1) shown in FIG. 3, gold(I) is shownto be coordinated with one P donor atom of tri-tert-butylphosphine and Sdonor atom of dibenzyldithiocarbamate ligand molecules. The Au—S andAu—P bond distances are 2.3365 (13) and 2.2824 (13) A respectively. TheAu—P and Au—S bond distances are comparable with [Et₃PAu(S₂CNEt₂)]complex [S. Y. Ho and E. R. T. Tiekink, Z. Kristallogr, 220 (2005)342—incorporated herein by reference in its entirety]. The geometryaround Au(I) metal atom is linear and similar to other analogous Au(I)complexes [I. Sanger, H.-W. Lerner, T. Sinke and M. Bolte, Acta Cryst.,E68 (2012) m708; P. Lu, T. C. Boorman, A. M. Z. Slawin and I. Larrosa,J. Am. Chem. Soc., 132 (2010) 5580; R. E. Marsh, Acta Cryst., B58 (2002)893; H. Schmidbaur, B. Brachthiuser, O. Steigelmann, and H. Beruda,Chem. Ber., 125(1992) 2705—each incorporated herein by reference in itsentirety]. S—Au—P bond angle is 178.33 (5°) in the molecular structureof [t-Bu₃PAuS₂CN(C₇H₇)₂] or Complex (A1) which is very close to angle of180° for ideal linear geometry. Hence, the complex (A1) shows a smalldeviation from ideal linear geometry around gold(I) atom (Table 4) andconfirms the presence of distorted linear geometry in this molecule.

TABLE 2 Crystallographic characteristics, experimental and structurerefinement details for crystal structure of Complex (A1). ParametersComplex 1 Empirical formula C₂₇H₄₁AuNPS₂ Empirical formula weight 671.66Crystal size/mm 0.45 × 0.30 × 0.07 Wavelength/Å 0.71073 Temperature/K173 Crystal symmetry Orthorhombic Space group Pbca a/Å 12.3157 (12) b/Å19.6569 (19) c/Å 22.945 (2) V/Å³ 6375.6 (4) Z 8 D_(c)/Mg m⁻³ 1.606μ(Mo-Kα)/mm⁻¹ 5.52 F(000) 2688 θ Limits/° 1.8-26.2 Collected reflections17654 Unique reflections 3454 Observed reflections 5296 Goodness of fiton F² 0.79 R₁[F² > 2σ(F²)] 0.028 wR₂(F²) 0.062 Largest diff. peak,hole/e Å⁻³ 1.08, −0.79

TABLE 3 Selected bond distances (Å) and bond angles (°) for Complex(A1). Bond Length (Å) Bond Angles (°) Au1—P1 2.2824 (13) P1—Au1—S1178.33 (5)  Au1—S1 2.3365 (13) C13—S1—Au1 100.26 (16) S1—C13 1.749 (5)C5—P1—C1 110.4 (2) S2—C13 1.701 (5) C5—P1—C9 110.4 (2) C1—P1—C9 109.7(2) C5—P1—Au1 110.40 (16) C1—P1—Au1 106.82 (18) C9—P1—Au1 109.03 (19)

Example 8 Chemistry and Spectroscopic Characterization of SynthesizedGold(I) Complexes

Addition of dibenzyl dithiocarbamate to tri-tert butylphosphine gold(I)chloride afforded the formation of mononuclear gold(I) crystallinecomplex (A1). Moreover, addition of dimethyl dithiocarbamate, diethyldithiocarbamate, dibenzyl dithiocarbamate to[μ-Bis(diphenylphosphino)methane]dichlorodigold(I) afforded theformation of three binuclear gold(I) complexes (A1)-(A3) respectively ingood yields. Binuclear bisphosphine gold(I) complexes (A2) and (A3)contain small alkyl groups i.e. methyl and ethyl in dialkyldithiocarbamate in order to examine the steric effects on anticanceractivities. On the other hand, mononuclear monophosphine gold (I)complex (A1) and binuclear bisphosphine gold(I) complex (A4) containbulky aryl group i.e. benzyl in diaryl dithiocarbamate to evaluate thesteric effects on in vitro cytotoxicity.

Dithiocarbamate compounds can be identified via the presence of certainabsorbance peaks primarily ν(C—N) and ν(C—S). The region 1480-1550 cm⁻¹is primarily associated with the R₂N—CSS ‘thioureide’ band in theinfrared spectra of dithiocarbamate compounds which defines thecarbon-nitrogen bond order between a single bond at 1250-1350 cm⁻¹ and adouble bond at 1640-1690 cm⁻¹ [A. J. Odola and J. A. O. Woods, J. Chem.Pharm. Res., 3 (2011) 865—incorporated herein by reference in itsentirety].

The distinctive thioureide band, ν(C—N) was detected at 1456 cm⁻¹, 1481cm⁻¹, 1486 cm⁻¹ and 1489 cm⁻¹ in complexes (A1)-(A4) respectively. Sincethese frequency modes lie in between those associated with single C—Nand double C═N bonds, hence the partial double bond character of‘thioureide’ bond was confirmed for all gold(I) complexes [F. Jian, Z.Wang, Z. Bai, X. You, H. Fun, K. Chinnakali and L. A. Razak, Polyhedron,18 (1999) 3401—incorporated by reference in its entirety]. The presenceof the ‘thioureide’ band between 1545-1430 cm⁻¹ suggest a considerabledouble bond character in the C . . . N bond vibration of the S₂C—NR₂group [A. Jayaraju, M. M. Ahamad, R. M. Rao, J. Sreeramulu, Der PharmaChemica, 4 (2012) 1191—incorporated herein by reference in itsentirety]. This strong absorption band (1542-1480 cm⁻¹) is known as thethioureide ion band. The band appears intermediate within C—N singlebond (C—N: 1063-1261 cm⁻¹) and double bond (C═N: 1640-1690 cm⁻¹) wavenumbers. Such characteristic band shows the partial double bond featurewhich characterizes the formation of dithiocarbamato (S₂C—NR₂)⁻ anion.The stretching vibration corresponds to this partial double bond due tothe partial delocalization of electron density within thedithiocarbamate [H. Nabipour, S. Ghammamy, S. Ashuri and Z. S.Aghbolagh, J. Org. Chem., 2 (2010) 75—incorporated herein by referencein its entirety]. A strong absorption in this region of the FTIRspectrum results into a strong signal of dithiocarbamato gold(I)complexes [J. Chatt, L. A. Duncanson and L. M. Venanzi, Nature, 177(1956)1042—incorporated herein by reference in its entirety].

The C═S thiocarbonyl stretching splits into two peaks (doublet) withmedium intensity at 1022 cm⁻¹ and 972 cm⁻¹; 1099 cm⁻¹ and 995 cm⁻¹; 1087cm⁻¹ and 982 cm⁻¹; and 1025 cm⁻¹ and 970 cm⁻¹ for complexes (A1)-(A4),respectively. The splitting of stretching band is found within the rangeof 1099-970 cm′ due to the prevailing contribution of (C . . . S). Suchsplitting in the ν(C—S) bands clearly indicates the monodentate natureof dialkyldithiocarbamate ligands in the synthesized complexes [I. Raya,I. Baba, B. M. Yamin, Malaysia J. Analytical Sciences (MJAS), 10 (2006)93; W. Haas, and T. Schwarz, Microchem. Ichonal. Acta, 58 (1963) 253; D.C. Onwudiwe and P. A. Ajibade, Polyhedron, 29 (2010) 1431—eachincorporated herein by reference in its entirety]. The spectroscopicdata suggests monodentate modes of coordination for the dithiocarbamateligands in complexes (A1)-(A4) in analogy of compound[(Ph₂P(CH₂)₂PPh₂)(AuS₂CNEt₂)₂ [J. W. Faamaua and E. R. T. Tiekinka, J.Coord. Chem., 31(2) (1994) 93—incorporated herein by reference in itsentirety].

In addition to the polar thioureide ion S₂C=N⁺R₂ band, the common bandsfor sp³ and sp² hybridized C—H stretches are observed within 2995-22917cm⁻¹ and above 3000 cm⁻¹ respectively which are very comparable to thoseof sodium salt of diethyldithiocarbamate [C. J. Pouchert, AldrichLibrary of FT-IR Spectra, 2nd ed., Aldrich Chemical Company, Milwaukee,1 (1997)—incorporated herein by reference in its entirety].

In complexes (A1) and (A4), the stretch bands of aromatic (phenyl) andthe saturated aliphatic C—H methyl group of coordinateddialkyl/diaryldithiocarbamate correspond above and below 3000 cm⁻¹. TheC—H methyl groups have characteristic bending absorptions at 1370 cm⁻¹and 1374 cm⁻¹ in complexes (A2) and (A3) respectively. The C—H bendingband(s) associated C—H stretching band(s) are often determining factorwhether methyl groups are present in a molecule or not. The coordinatedC—H(—CH₂—) methylene stretching bands of diethyl dithiocarbamate anddibenzyl dithiocarbamate occur at 2983 cm⁻¹, 2921 cm⁻¹ and 2919 cm⁻¹respectively; and their corresponding bending bands appears at 1378cm⁻¹, 1432 cm⁻¹ and 1332 cm⁻¹ for complexes (A1), (A3) and (A4)respectively [D. L. Pavia, G. M. Lampman, S. G. Kriz, Introduction toSpectrochemistry, 3rd Ed., Thomson Learning, USA, (2001) 30; R. M.Silverstein, F. X. Webster, Spectrometric Identification of OrganicCompounds, 6th ed., (Wiley, New York, 1998); T. W. G. Solomons, C.Fryhle Organic Chemistry, 7th ed., Wiley, New York, 2001; K. N.Kouroulis, S. K. Hadjikakou, N. Kourkoumelis, M. Kubicki, L. Male, M.Hursthouse, S. Skoulika, A. K. Metsios, V. Y. Tyurin, A. V. Dolganov, E.R. Milaevag and N. Hadjiliadis, Dalton Trans., (2009) 10446; E. A. Allenand W. Wilkinson, Spectrochim. Acta, 2 (1972) 2257; I. S. Butler, A.Neppel, K. R. Plowman and C. F. Shaw, J. Raman Spectrosc., 15 (1984)310; A. G. Jones and D. B. Powell, Spectrochim. Acta, 30 (1984) 563—eachincorporated herein by reference in its entirety].

The ¹H NMR chemical shifts of metal precursors [t-Bu₃PAuCl],[(DPPM)(AuCl)₂] and free dialkyl/diaryldithiocarbamate ligands are givenin Table 1. Small upfield and downfield shifts for the mono andbisphosphine coordinated ligands protons have been observed forcomplexes (A1)-(A4); with respect to the chemical shifts of free metalprecursor as given in synthesis part of experimental section for thesecomplexes. In all four complexes slight downfield and upfield shifts forproton(s) of the coordinated dimethyl dithiocarbamate, diethyldithiocarbamate and dibenzyldithiocarbamate have also been seen ingold(I) complexes (A1)-(A4) respectively in comparison to freedialkyl/diaryldithiocarbamate ligands (Table 1).

The ¹³C and ³¹P NMR chemical shifts of metal precursors[t-Bu₃PAuCl],[(DPPM)(AuCl)₂] and free dialkyl/diaryldithiocarbamate ligands are givenin Table 2. The ¹³C NMR spectra of complexes (A1)-(A4) showed manyresonances as given in synthesis part of experimental section for thesecomplexes. There are up-field chemical shifts of CH₃, CH₂ and C═Scarbons of coordinated dialkyldithiocarbamate with respect to freedialkyl/diaryldithiocarbamate ligands. The ¹³C chemical shifts of C═Scarbon of dimethyl thiocarbamate, diethyl thiocarbamate and dibenzylthiocarbamate are observed in the range 206-210 ppm. The upfield shiftsof C═S carbon are additional confirmations for the coordination ofdialkyl/diaryl dithiocarbamates ligands in the synthesized complexes(A1)-(A4).

Example 9 Cell Cultures

A549, HeLa and HCT15 human cancer cells were seeded and maintained intriplicate at 4×10³ cells/well in 100 μL DMEM (Dulbecco's ModifiedEagle's Medium) containing 10%. FBS (Fetal Bovine Serum) in 96-wellstissue culture plate and incubated for 72 h at 37° C., 5% CO₂ in air and90% relative humidity in CO₂ incubator.

Example 10 MTT Assays for Anticancer Activity of Cisplatin, Gold(I)Precursor Complex A0 and Synthesized Gold(I) Complexes A1-A4

100 μL of cisplatin, gold(I) precursor Complex A0 and gold(I) Complexes(A1)-(A4) in 50, 25, 12.5 and 6.25 μg/mL concentrations, prepared inDMEM, were added to 5000 cancer cells after incubation. The resultantcultures were incubated for 24 h. The medium of wells was discarded. 100μL DMEM containing MTT(3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide) (5 mg/mL)was added to the wells and incubated in CO₂ incubator at 37° C. in darkfor 4 h. After incubation, a purple colored formazan (artificialchromogenic dye, product of the reduction of water insoluble tetrazoliumsalts e.g., MMT by dehydrogenases and reductases) in the cells isproduced and appeared as dark crystals in the bottom of the wells. Themedium of culture was discarded from each well carefully to avoiddisruption of monolayer. 100 μL of Dimethylsulphoxide (DMSO) was addedin each well. The solution was thoroughly mixed in the wells to dissolvethe formazan crystals which ultimately result into a purple solution.The absorbance of the 96-wells plate was taken at 570 nm with Labsystems Multiskan EX-Enzyme-linked immunesorbent assay (EX-ELISA) readeragainst a reagent blank. All data presented are mean±standard error ofthe mean (SEM).

The concentration (dose) dependent in vitro cytotoxic effect wasobtained by the specific increase in concentrations of cisplatin,gold(I) precursor (A0) and gold(I) Complexes (A1)-(A4) against a panelof human cancer cells. The viability of HeLa, HCT15 and A549 cancercells versus concentrations of gold(I) complex is graphically presentedin FIGS. 4, 5 and 6, respectively. Gold(I) precursor (A0) andsynthesized complexes (A1)-(A4) invariably inhibited the proliferationof all cancer cells in a concentration dependent manner. Generally, thegrowth inhibition of cancer cells is higher for the synthesizedcomplexes (A1)-(A4) in comparison to that of gold(I) precursor (A0).Particularly, the degree of anti-proliferation of gold(I) of thesynthesized complexes (A2) and (A3) is significantly greater than thoseof the synthesized complexes (A1) and (A4) as illustrated in FIGS. 4-6.

The IC₅₀ values for cisplatin, gold(I) precursor (A0) and complexes(A1)-(A4) against three cancer lines are given in Table 4. The IC₅₀ datafor the synthesized gold(I) complexes (A1)-(A4) against selected humancancer cell lines i.e. A549, HeLa and HCT15 are in the range of 1.3 to132.7 μM. For comparative purposes, the IC₅₀ values of cisplatin for thesame cell lines were also included.

TABLE 4 IC₅₀ data (μM) of cispaltin and gold(I) complexes (0-4) againstA549, HeLa and HCT15 cancer cell lines. IC₅₀ (μM) Complex A549 HeLaHCT15 Cisplatin 41.6 19.4 29.5 [(DPPM)(AuCl)₂] (A0) 136.6 108.5 148 (A1)96.9 25.6 93.2 (A2) 5.4 1.3 9.5 (A3) 8.6 1.6 11.8 (A4) 105.8 93.2 132.7

The IC₅₀ values against A549 cell line were found to be 41.6, 136.6,96.9, 5.4, 8.6 and 105.8 μM for cisplatin, gold (I) precursor (A0) andcomplexes (A1)-(A4) respectively. It is inferred from the IC₅₀ data thatin vitro cytotoxicity of complexes (A2) and (A3) is significantlygreater 15-25 times than gold (I) precursor (A0); and 5-8 times thancisplatin respectively. The IC₅₀ values of cisplatin, precursor (A0) andgold complexes (A1)-(A4) against HeLa cell line were found to be 19.4,108.5, 25.6, 1.3, 1.6 and 93.2 μM respectively. A similar trend has beenobserved in HeLa cell line that in vitro cytotoxicity of complexes (A2)and (A3) in terms of IC₅₀ is improved almost 75 folds than gold (I)precursor; and 12-15 folds than cisplatin respectively. IC₅₀ values ofcisplatin, gold precursor (A0), gold complexes (A1)-(A4) against HCT15cell line were 29.5, 93.2, 9.5, 11.8, 132.7 and 148.0 μM respectively.Similarly, to A459 and HeLa cell lines, in vitro cytotoxicity ofcomplexes (A2) and (A3) in terms of IC₅₀ is enhanced 12-16 times thangold (I) precursor; and 2-3 times than cisplatin. In short, the order ofin vitro cytotoxicity is (A2)>(A3)>cisplatin>(A1)>(A4)>precursor (A0)against A549, HeLa and HCT15 cancer cell lines. It is pertinent tomention that the effectiveness trend of complexes (A2) and (A3) in termsof in vitro cytotoxicity against three cell lines is HeLa>A549>HCT15. Itcan be concluded from this studies that complexes (A2) and (A3) are themost effective cytotoxic agents against HeLa cancer cell line.

As far as the in vitro cytotoxicity against A549, HeLa and HCT15 celllines is concerned, two out of four synthesized complexes (A2) and (A3)show much better anticancer activity than classical and well knownanticancer drug cisplatin. The much better inhibition of growth ofcancer cells by synthesized complexes than gold(I) precursor complex canbe attributed to dithiocarbamate as labile co-ligands bonded withcentral gold(I) ions in synthesized complexes (A1)-(A4) by replacingchloride ions in these mononuclear and binuclear complexes.

As known in the art of drug design and discovery; selectivity andinhibition of target biomolecules is very important. In this regard thein vitro cytoxicity results in the present disclosure are fruitful andvery encouraging for further exploration of anticancer activity ofgold(I) complexes. In short, the IC₅₀ values of gold(I) complexes (A2)and (A3) having dialkyldithiocarbamate ligands show much bettercytotoxicity than gold(I) complexes (A1) and (A4) havingdiaryldithiocarbamate ligands. The lower cytotoxic activity of gold(I)complexes (A1) and (A4) is due to bulky size and steric hindrance ofdiarylthiocarbamate ligands. The steric hindrance of bulky ligand makesthe approach of gold(I) ions difficult to biomolecules in thesecomplexes. Overall the anticancer activity of synthesized complexesagainst A549, HeLa and HCT15 human cancer cell lines are interesting andin μM range as found in previous anticancer studies of gold complexes[E. Barreiro, J. S. Casas, M. D. Couce, A. Sánchez, J. Sordo and E. M.Vázquez-López, J. Inorg. Biochem., 131 (2014) 68; R. Kivekäs, E.Colacio, J. Ruiz, J. D. López-González and P. León, Inorg. Chim. Acta.,159 (1989) 103; L. Ortego, F. Cardoso, S. Martins, M. F. Fillat, A.Laguna, M. Meireles, M. D. Villacampa and M. C. Gimeno, J. Inorg.Biochem., 130 (2014) 32; I. Ott, T. Koch, H. Shorafa, Z. Bai, D.Poeckel, D. Steinhilber and R. Gust, Org. Biomol. Chem., 3 (2005)2282—each incorporated herein by reference in its entirety].

Thus, the foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. As will be understood by thoseskilled in the art, the present invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Accordingly, the disclosure of the presentinvention is intended to be illustrative, but not limiting of the scopeof the invention, as well as other claims. The disclosure, including anyreadily discernible variants of the teachings herein, defines, in part,the scope of the foregoing claim terminology such that no inventivesubject matter is dedicated to the public.

1: A composition comprising: a gold(I) complex having Formula 3, or apharmaceutically acceptable salt or ester thereof, at least one proteinkinase inhibitor, and a hydrophobic carrier, wherein Formula 3 is:

2-5: (canceled) 6: The composition of claim 1, wherein the compositionis in a solid, semi-solid, or liquid dosage form. 7: The composition ofclaim 1, wherein the composition is formulated for one or more modes ofadministration selected from the group consisting of oraladministration, systemic administration, parenteral administration,inhalation spray, infusion, rectal administration, topicaladministration, intravesical administration, intradermal administration,transdermal administration, subcutaneous administration, intramuscularadministration, intralesional administration, intracranialadministration, intrapulmonal administration, intracardialadministration, infrasternal administration and sublingualadministration. 8: A method for inhibiting proliferation of cancercells, comprising: contacting the cancer cells with the composition ofclaim
 1. 9: The method of claim 8, wherein the cancer cells are humancells. 10: The method of claim 8, wherein the cancer cells are at leastone selected from the group consisting of lung cancer cells, colorectalcancer cells and cervical cancer cells. 11: The method of claim 8,wherein the gold(I) complex concentration is 5-50 μM. 12: The method ofclaim 8, wherein the gold(I) complex exhibits an IC₅₀ of 1-150 μM forinhibiting the proliferation and inducing the apoptosis of the cancercells. 13: The composition of claim 1, further comprising at least onechemotherapeutic agent selected from the group consisting ofaflibercept, asparaginase, bleomycin, busulfan, carmustine,chlorambucil, cladribine, cyclophosphamide, cytarabine, dacarbazine,daunorubicin, doxorubicin, etoposide, fludarabine, gemcitabine,hydroxyurea, idarubicin, ifosfamide, irinotecan, lomustine,mechlorethamine, melphalan, mercaptopurine, methotrexate, mitomycin,mitoxantrone, pentostatin, procarbazine, 6-thioguanine, topotecan,vinblastine, vincristine, retinoic acid, oxaliplatin, carboplatin,5-fluorouracil, teniposide, amasacrine, docetaxel, paclitaxel,vinorelbine, bortezomib, clofarabine, capecitabine, actinomycin D,epirubicin, vindesine, methotrexate, and tipifarnib. 14: The compositionof claim 1, further comprising at least one antineoplastic antibodyselected from the group consisting of trastuzumab, cetuximab,panitumumab, rituximab, bevacizumab, mapatumumab, conatumumab, andlexatumumab. 15: The composition of claim 1, wherein the at least oneprotein kinase inhibitor treats at least one cancer selected from thegroup consisting of lung cancer, colorectal cancer, and cervical cancer.16: The composition of claim 1, wherein the at least one protein kinaseinhibitor is selected from the group consisting of imatinib, erlotinib,sorafenib, sunitinib, dasatinib, nilotinib, lapatinib, gefitinib,temsirolimus, everolimus, rapamycine, bosutinib, pzopanib, axitinib,neratinib, vatalanib, pazopanib, midostaurin, and enzastaurin. 17: Thecomposition of claim 15, wherein the at least one protein kinaseinhibitor treats lung cancer. 18: The composition of claim 16, whereinthe at least one protein kinase inhibitor is erlotinib, gefitinib, orboth. 19: The composition of claim 1, wherein the hydrophobic carrier isa vegetable oil, a vegetable fat, or both. 20: The composition of claim19, wherein the vegetable oil is at least one selected from the groupconsisting of corn oil, cottonseed oil, peanut oil, and sesame oil. 21:The composition of claim 19, wherein the vegetable fat is cocoa butter.22: The composition of claim 1, which consists essentially of thegold(I) complex, the protein kinase inhibitor, and the hydrophobiccarrier. 23: The composition of claim 1, which consists of the gold(I)complex, the protein kinase inhibitor, and the hydrophobic carrier.